Rotary control valves have a shaft member that is driven rotatably to position the valve control member in the proper position for the requested function. Rotary valves have been proposed for use in automatic shifting power transmissions to control the position of the manual control valve during operation of the transmission. For example, the valve control member has a reverse position, a neutral position and a plurality of forward drive positions. The control member has to respond to both clockwise and counterclockwise rotary input commands.
In one control system, the piston has a pair of one way clutch members disposed between a shaft and the piston to effect a drive connection therebetween depending on the desired direction of rotation. The one-way mechanisms are hydraulically actuated to establish a drive connection and both must be released to permit the piston to return to a central position. In another rotary valve system the piston is driven to specific stops by the hydraulic control. This requires a number of hydraulic control ports to support each stop position or a piston having multiple components. A hydraulic control system having a single control piston is described in U.S. Ser. No. 09/105,405 filed Jun. 26, 1998 and assigned to the assignee of this application.